How can I load Myriad Pro font onto my new iMac?

I just did this process on my Mac mini after seeing your post to see if it was possible. It's really not a hard process, you'll need to download the font which a google search will get you where you need to go to download it. Once you get it downloaded you can check out the instructions here Install and validate fonts in Font Book on Mac - Apple Support. It's just a matter using spotlight (command + space) to bring up "font book" and then File > Add fonts to current user. Then pointing the computer to where you saved the font and it will validate that it will work and adds it.